In the field of prosthodontics, orthopedic joint prosthetics and dental implantology it has been found that the compatibility of the materials used for prostheses with biological tissues is fundamentally important to allow adequate treatment of the patients.
The materials commonly used in these fields consist substantially of metallic substrates of steel titanium or tantalum, which have excellent mechanical properties but require long times for integration in the biological tissues of the patients, in which they are implanted and for healing of the implantation region.
In order to overcome these drawbacks, methods have been developed which are suitable to modify the surface topography and chemistry of the metallic substrates by introducing thereon chemical groups or chemical elements capable of interacting with biological tissues and thus allowing integration between the prosthesis and the tissues. These methods are able to modify the surfaces reproducing the chemical composition and/or the topographical aspect of the tissue in which the material will be in contact in the biological environment. These methods are generally known as biomimetic treatments. For example U.S. Pat. No. 5,385,662 describes the modification of metallic surfaces by means of a hydrogen peroxide treatment in order to deposit a layer of metallic oxides on said surfaces. This method, however, is not described for use in the biomedical field. U.S. Pat. Nos. 5,152,993 and 5,885,612 describe a treatment of metallic surfaces by using hydrogen peroxide and optionally metallic ions in order to modify the surfaces of metallic prostheses by introducing hydroxyl (—OH) groups thereon.
EP068300, on the other hand, describes the treatment of metallic surfaces by immersion in alkaline solution of NaOH, followed by washing and high temperature thermal treatment. This method, too, introduces —OH groups, which are suitable for interaction with bone tissues, on the treated metallic surface.
Moreover U.S. Pat. No. 5,478,237 describes the use of anodic deposition on the surface of bone implants with the object of modifying the composition and morphology of the metallic substrate. Although the introduction of —OH groups is not described, the process of U.S. Pat. No. 5,478,237 leads to the formation of a porous layer rich in calcium and phosphorous on the surface of implants facilitating the osteointegration thereof.
EP 1,515,759 in the name of the Applicant teaches the use of a double step of anodic deposition to deposit on the surface of the metallic implant a microporous layer of calcium and phosphorus, and at the same time introducing —OH groups.
An improvement to the technology disclosed in the above patents is disclosed in EP2307594 as it allows to introduce on the surface of the metallic substrate by ASD deposition of chemical elements, such as Ca, P, Si, and Na that are suitable to increase the biomimetic properties of the surface modified metallic substrate and also provide —OH groups with a successive treatment with an NaOH solution of the substrate coming from ASD deposition, without resorting to multiple anodic layers deposition as described in the aforementioned method of EP1,515,759.
Although the technology described in EP2307564 represents a considerable improvement if compared to the prior art of metallic substrates used for osteointegrative purposes, it does not solve the problem connected with the insurgence of bacterial infections.
Clinical practice reports that bacterial infections occurring in implanted devices represents one of the commonest causes of failure of these implanted devices: with the consequent removal of the same implant from the host organism and replacement thereof bring to an increase of health care costs as well as social costs, also taking into account that the antibiotic and pharmacologic treatment results in most cases ineffective in this field.
CN101862269 abstract describes an implant in titanium enriched with only calcium and phosphorus having on the surface grains of Ag in the form of nanoparticles which is provided with antibacterial activity, however it is not clear from the abstract the technique used to obtain this implant.
To date metallic substrates obtained by ASD technique possessing both a high osteointegrative activity and contemporaneously showing antibacterial properties are not available, since the surface treatments of metallic substrate are directed to limit the adhesion or proliferation of bacteria, but they result not possessing any osteointegrative activity as in most cases they resulted toxic for the eukaryotic cells of the host's tissue.
Therefore an object of the invention is to modify the morphology of the metallic substrates, giving them a structure that is suitable for interacting in an optimal level with biological tissues and contemporaneously shows antibacterial properties.
Another object of the invention is to provide a biomimetic treatment of metallic substrates, that is highly reliable, relatively easy to be provided and at competitive costs.
Therefore a further subject of the present invention relates to a prosthesis or a component thereof or an implant comprising or completely made of this material.